enthusiasm was checked by my anxiety

This poses a contrast worth contemplating: on the one hand, as earlier in
the chapter (1.3.6 and note), enthusiasm
here literally suggests the presence of an indwelling deity, or at least
Victor's aspiration to play God; on the other hand, anxiety indicates a
counterforce within his mind, disrupting his self-assurance, even
prompting self-alienation. Since in Milton's myth Satan is created as a
counterforce at the precise moment that God announces his plan to create a
new race, these contrary poles are essential to the basic creation myth
in terms of which Mary Shelley plots her novel.

This is the angel Raphael's account of the beginning of the new universe
in Paradise Lost, V.579-617.